States of Matter

because plaster of Paris has a property of setting into a hard mass on getting mixed with water due to the formation of a new compound. The hard mass cannot be converted back into the previous plaster of Paris.

Changes that can be reversed is called reversible changes.

Air is a mixture of gases, primarily nitrogen (78%), oxygen (21%), and trace gases like argon, carbon dioxide, and water vapor. A mixture can be separated by physical means, unlike a compound which has fixed chemical bonding. The composition of air varies slightly with location and altitude, confirming it's a mixture rather than a compound.

The chemical reactions in all plants and animals that support life take place in as water medium. Water not only provides medium to make these reactions possible but is itself an important reactant or product of these reactions. Water is thus an important universal solvent. It consists of 2 hydrogen atoms and one oxygen atom which are held together by covalent bonds. Oxygen is more electronegative than hydrogen molecules. Hydrogen is positively charged and oxygen is negatively charged. Thus it can dissolve and dissociate most of the compounds. Positive part will be attracted towards oxygen and negative part of the compound towards hydrogen.

Condensation is process in which water vapours present in atmosphere are changed or cooled down to form water droplets. These water droplets combine together to form clouds. Thus clouds are composed of millions of little droplets of water.

Water drops appear on the outer surface of glass containing cold water. The cold surface of the glass containing cold water cools the air around it, and the water vapour of the air condenses to form water droplets on the surface of the glass. Thus, it is a process of change of gaseous state into liquid state.

All the choices given i.e. evaporation, transpiration and condensation are natural phenomena. Crystallization is a process of formation of crystals by boiling a liquid and then cooling it until gets solidify into a crystalline solid either by natural process or artificially. Ice crystals are formed naturally by the freezing of water. So crystallization is an artificial process.

Milk is an emulsion - specifically, it's an oil-in-water emulsion where fat globules are dispersed in water. Emulsions are colloidal systems where one liquid is dispersed as droplets in another immiscible liquid, stabilized by emulsifying agents like casein proteins in milk.

Sublimation is the phase transition from solid directly to gas (or vice versa) without passing through the liquid phase. Only the physical state changes - the chemical identity remains unchanged. Oxidation, reduction, and decomposition are all chemical changes.

A substance which changes readily into vapour without heating is called volatile (option C). Volatile substances have high vapor pressure at room temperature and evaporate easily. Efflorescent substances lose water of crystallization, effervescent substances release gas bubbles, and synthetic refers to artificially made materials.

Pure water undergoes self-ionization: H2O ⇌ H+ + OH-. At 25°C, the concentrations of H+ and OH- are equal (10^-7 M each), resulting in neutral pH. This balanced dissociation makes water neither acidic nor alkaline.

 This is the correct option. Condensation is the change in the state of water vapor to liquid water when in contact with any surface. Condensation is crucial to the water cycle because it is responsible for the formation of clouds.

This is a property of metals like gold, in which it can be beaten into sheets and drawn into wire. Water has no such property.

Water is used as coolant in car radiators because it has high specific heat capacity of 4200 Joules. Due to its high specific heat capacity, it can absorb a large amount of heat energy from the engine of the car, but its temperature does not rise too high.